The present invention relates to a method of fabricating a super-resolution optical panel applicable to an optical disc player and the like, and particularly, to a method of fabricating a super-resolution optical panel having a high optical utilization ratio and capable of electrically changing over a numerical aperture with ease, suitable for implementation of an optical pickup for common use in DVDs (digital versatile discs) and CDs (compact discs).
There has already been developed a liquid crystal lens capable of varying a focal length by an applied voltage as disclosed in, for example, JP, 4-240817, A.
As shown in FIG. 40, a variable focal length liquid crystal lens disclosed in this publication has a construction wherein 320xc3x97220 pixels are arranged in a lattice shape by use of transparent electrodes in a display area 102 which is recorded as a phase type Fresnel zone plate 101 of a liquid crystal space optical modulator 100, and liquid crystal of an ECB (electrically controlled birefringence) mode is sealed in the display area 102.
The liquid crystal space optical modulator 100 has a light wave modulation characteristic such that laser beams undergo continuous phase modulation in a range of 0 to 2xcfx80 when a voltage is applied to the transparent electrodes.
At the time of such phase modulation, by applying a voltage signal Vs that affects every pixel with phase modulation corresponding to the spatial coordinates thereof, laser beams 103 incident on the liquid crystal space optical modulator 100 undergo phase modulation by every pixel, and are concentrated at a focal point Fa on the optical axis as shown in FIG. 41.
Further, if a different voltage signal Vs is applied thereto, the light concentrating position of the laser beams 103 can be moved to a point Fb on the optical axis.
However, the publication described above discloses merely a theoretical configuration, and in the embodiments described therein, no description on a shape, construction, material, and so forth of the liquid crystal space optical modulator has been given in concrete terms, so that the invention cited has not been practicable.
Also, a liquid crystal lens is disclosed in JP, 3-2840, A. Referring to FIG. 42, the liquid crystal lens is briefly described hereinafter. The liquid crystal lens comprises a liquid crystal, a control electrode for applying a voltage to the liquid crystal, and a fixed electrode, and as shown in FIG. 42, the control electrode 105 is comprised of transparent electrode bands 106 in a circular and concentric ring-like shape, and insulating bands 107 for insulating the respective transparent electrode bands 106 from each other. The respective transparent electrode bands 106 are independently wired.
When a voltage is applied to the transparent electrode bands 106, the polarization plane of incident light is rotated through 90 degrees in areas where the transparent electrode bands 106 exist during a period when the incident light passes through a liquid crystal layer while the incident light is permitted to pass therethrough as it is in other areas.
Accordingly, light beams outgoing from the liquid crystal lens form images at an identical point independently without interfering with each other, and the focal point length of the liquid crystal lens is varied by a voltage applied to the transparent electrode bands 106.
However, description on a shape, material, and so forth, thereof is not set forth in practicable and concrete terms in this publication, and a method of fabricating the same is not available therein either, so that the invention cited has not so far been practiced.
Further, it has been theoretically shown that a super-resolution optical panel can be obtained by making use of a liquid crystal panel, and by differentiating the alignment direction of a portion of a light transmitting region thereof from that of other regions thereof. However, the super-resolution optical panel has not so far been put to commercial use, because the super-resolution optical panel has been unable to be fabricated at a high yield and at a low cost.
It is therefore an object of the invention to overcome the problems described above, and to provide a method of fabricating a super-resolution optical panel capable of varying intensity of laser beams with ease at a high yield and low cost.
To this end, a method of fabricating a super-resolution optical panel according to the present invention comprises:
a step of preparing a first substrate and a second substrate, both of which are transparent;
a step of forming a first circular transparent electrode on the first substrate;
a step of forming a second circular transparent electrode larger than the first circular transparent electrode on the second substrate;
a step of forming an alignment layer in a region covering at least the first circular transparent electrode on the first substrate, and in a region covering at least the second circular transparent electrode on the second substrate, respectively;
a step of applying an alignment treatment in a first direction to the respective alignment layers by use of a rubbing roll such that pre-tilt faces of the respective alignment layers are in parallel with each other when the first circular transparent electrode is opposed to the second circular transparent electrode;
a step of forming a resist patterned in a doughnut-like shape provided with an opening in a circular shape at the center thereof on the alignment layer of the second substrate with a rubbing treatment applied thereto;
a step of applying an alignment treatment in a second direction orthogonal to the first direction to a portion of the alignment layer exposed inside the opening of the resist by use of a rubbing roll;
a step of subsequently peeling off the resist from the upper face of the second substrate;
a step of forming a sealing member on the first substrate so as to encircle the first circular transparent electrode;
a step of scattering gap members in a region encircled by the sealing member on the first substrate;
a step of bonding the first substrate with the second substrate so as to overlap each other with the gap members interposed therebetween by opposing the first circular transparent electrode to the second circular transparent electrode such that respective centers thereof coincide with each other, and the respective first directions in which the alignment treatment is applied to the respective alignment layers coincide with each other; and
a step of filling twisted nematic liquid crystal in a spacing encircled by the sealing member, and between the first substrate and the second substrate.
In accordance with a first aspect of the invention, it is preferable that,
in the step of forming the first circular transparent electrode on the first substrate, a first take-out electrode for connecting the first circular transparent electrode to an external terminal, and an isolated second take-out electrode are formed on the first substrate,
in the step of forming the second circular transparent electrode on the second substrate, a third take-out electrode for connecting the second circular transparent electrode to the second take-out electrode is formed on the second substrate, and
the method of fabricating the super-resolution optical panel further comprising a step of installing an electrically conductive adhesive on the third take-out electrode formed on the second substrate, subsequently to the step of scattering gap members,
wherein the second take-out electrode and the third take-out electrode are connected with each other by the electrically conductive adhesive in the step of bonding the first substrate with the second substrate so as to overlap each other.
Or the invention may be modified such that,
in the step of forming the first circular transparent electrode on the first substrate, a first take-out electrode for connecting the first circular transparent electrode to an external terminal, and an isolated second take-out electrode are formed on the first substrate,
in the step of forming the second circular transparent electrode on the second substrate, a third take-out electrode for connecting the second circular transparent electrode to the second take-out electrode is formed on the second substrate,
in the step of forming the sealing member on the first substrate, an anisotropic electrically conductive sealing member is formed so as to encircle the first circular transparent electrode and pass on the second take-out electrode, and
in the step of bonding the first substrate with the second substrate so as to overlap each other, the second take-out electrode and the third take-out electrode are connected with each other by the anisotropic electrically conductive sealing member.
Further, with these features, in the step of forming the first circular transparent electrode on the first substrate, a central circular transparent electrode in a small circular shape and a ring-like transparent electrode provided with a gap interposed therebetween may be formed on the first substrate in place of the first circular transparent electrode.
Further, a fourth take-out electrode and a first take-out electrode for connecting the central circular transparent electrode in the small circular shape and the ring-like transparent electrode to external terminals, respectively, together with an isolated second take-out electrode are preferably formed.
Furthermore, with the method of fabricating the respective super-resolution optical panels described above, the step of forming the resist, patterned in the doughnut-like shape provided with the opening in the circular shape at the center thereof on the alignment layer of the second substrate with the rubbing treatment applied thereto preferably comprises steps of:
applying a positive photosensitive resist onto the alignment layer of the second substrate with the rubbing treatment applied thereto;
subjecting the positive photosensitive resist to exposure by use of a photo mask having a through-hole in a circular shape at the center thereof;
subsequently developing the positive photosensitive resist by immersing the second substrate in a developing solution and dissolving a circular portion at the center of the positive photosensitive resist exposed to light, and
forming a resist patterned in a doughnut-like shape by baking and curing a remaining portion of the positive photosensitive resist in a doughnut-like shape.
In the case of fabricating a multiple pieces of the super-resolution optical panels at a time with the use of a pair of the first substrate and the second substrate, both being transparent, in accordance with any one of the methods of fabricating the respective super-resolution optical panel as described above, it is preferable that
in the step of forming the sealing member on the first substrate so as to encircle the first circular transparent electrode, a first sealing member having a filling hole is formed in such a way as to encircle the first circular transparent electrode of the individual super-resolution optical panels, and a second sealing member having a filling hole is formed in such a way as to enclose an entire region where all the super-resolution optical panels are formed,
in the step of filling the twisted nematic liquid crystal in the spacing encircled by the sealing member, and between the first substrate and the second substrate, the twisted nematic liquid crystal is filled into the spacing encircled by the respective first sealing members of all the super-resolution optical panels through the filling hole of the respective first sealing members by filling the twisted nematic liquid crystal through the filling hole of the second sealing member, and
subsequently, the first substrate and the second substrate are cut into a size of the individual super-resolution optical panels, respectively, and the filling hole of the first sealing member of the respective super-resolution optical panels as cut are closed with an adhesive.
Operation
With the super-resolution optical panel fabricated by the method according to the invention, high performance variation in intensity of light power at a focused spot can be effected by the agency of the central circular transparent electrode installed on the first substrate, and the ring-like transparent electrode concentrically installed on the outside of the central circular transparent electrode.
Further, with the method of fabricating the super-resolution optical panel according to the invention, a twisted alignment treatment is applied on the central circular transparent electrode, and a parallel alignment treatment is applied on the ring-like transparent electrode concentrically installed on the outside of the central circular transparent electrode, so that it becomes possible to vary intensity of transmitting laser light at a focused spot such that it is reduced when no voltage is applied while it is increased when a voltage is applied.
Also, as a step of printing on one side with silver paste can be eliminated as a result of mixing electrically conductive particles in the sealing member, fabrication steps can be simplified, resulting in reduction of a fabrication cost.